What action was successfully performed using the fertile F1 hybrids and one of the parental species?

Answer

Backcrossing

The research extended to backcrosses, where the F1 hybrids were mated back to one of the parent species, specifically the Red deer, and also successfully mated back to the Père David's deer.

What action was successfully performed using the fertile F1 hybrids and one of the parental species?
speciesanimaldeerhybrid